Vacuum pickup apparatus

ABSTRACT

A VACUUM PICKUP APPARATUS IN WHICH A STREAM OF AIR AND ENTRAINED MATERIAL FLOWING INTO AN EXPANSION AND MATERIAL COLLECTION CHAMBER STRIKES A CONCAVE SURFACE FLOW OBSTRUCTION AND IS DIVIDED INTO TWO PORTIONS DIRECTED ON OPPOSITELY TURNING COURSES OF FLOW FOR DISSIPATION OF THE KINETIC ENERGY OF THE INFLOWNG AIR AND ENTRAINED MATERIAL BY IMPINGEMENT OF THE PORTIONS FIRST AGAINST THE OBSTRUCTION AND THEN AGAINST EACH OTHER WITHIN THE CHAMBER. THE CAPACITY OF THE MATERIAL COLLECTION CHAMBER MAY BE VARIED BY SELECTIVE ARRANGEMENT AND INTERCONNECTION OF THREE HOUSING MEMBERS INCLUDED IN THE VACUUM PICKUP APPARATUS.

NOV- 9, 19.71 J. c. HAMRICK VACUUM PICKUP APPARATUS 4 Sheets-Sheet 1 Filed July 22, 1969 INVENTOR; JAMFJ C. HM R ICH ATTORNEYS Nov. 9, 1971 J. c. HAMRICK 3,618,297

VACUUM PICKUP APPARATUS Filed July 22, 1969 4 Sheets-Sheet 2 INVENTOR'. JAMES C. HAMRICK ATTORNEYS NOV. 9, 1971l J, Q HAMR|CK 3,618,297

VACUUM PICKUP APPARATUS Filed July 22, 1969 4 SheelZS-Slflel'I 5 JAMES C HAMRIQK ATTORNEYS Nov. 9, 1971 J. c. HAMRlcK VACUUM PICKUP APPARATUS 4 Sheets-Sheet 4 Filed July 22, 1969 INVENTOR JAME C. HAMRICK Unted States Patent @moe 3,618,297 VACUUM PICKUP APPARATUS James C. Hamrick, Matthews, N.C., assigner to .let Line Products, Inc., Matthews, N.C. Filed July 22, 1969, Ser. No. 843,364 Int. Cl. Btlld 50/00 U.S. Cl. 55--216 16 Claims ABSTRACT F THE DISCLOSURE A vacuum pickup apparatus in which a stream of air and entrained material flowing into an expansion and material collection chamber strikes a concave surface flow obstruction and is divided into two portions directed on oppositely turning courses of How for dissipation of the kinetic energy of the inowing air and entrained material by impingement of the portions rst against the obstruction and then against each other within the chamber. The capacity of the material collection chamber may be varied by selective arrangement and interconnection of three housing members included in the vacuum pickup apparatus.

Air ow inducing means are now being used to suck or blow plugs through tubing elements such as electrical wiring conduits, for purposes of trailing cords or the like through the conduits to assist in pulling electrical conductors thereinto. Where the air ow inducing means is used in applying suction to a conduit to draw a plug therethrough, any foreign material within the conduit is entrained by air flowing to the air flow inducing means and is picked up by the apparatus. Electrical wiring conduits installed in a building under construction frequently trap and contain Water as well as solid debris generated by construction work, and thus present a particularly hostile environment of use. Any air tlow inducing means used as a vacuum apparatus in this environment will pick up such material from within the conduit and must be capable of separating both liquid and solid materials from air ow in order to properly operate.

Heretofore, the quantities of Water entrapped within an electrical conduit system have presented particular diiculty as trapped water quantities may be relatively large if the construction project in which the conduit is located has been exposed to rainy weather. In such circumstances, the vacuum pickup apparatus desirably is not only fully capable of separating entrained liquid from air owing therethrough but additionally has the capacity to retain a significant volume of separated liquid. Certain vacuum pickup apparatus heretofore proposed for use in the environment herein described have encountered difficulty in that the means for separating entrained liquid from air flowing through the apparatus results in signicant turbulence of Water collected, raising the danger of splashing water into the air ow inducing means or fan and severely restricting the capacity of liquid which can be retained.

In view of the above, it is an object of the present invention to separate entrained materials, and particularly entrained liquids, from air owing through a vacuum pickup apparatus in a manner which least contributes to turbulence Within the apparatus and thereby decreases the likelihood that liquid will be splashed into the means which induces ow of air through the apparatus. In

3,618,297 Patented Nov. 9, 1971 realizing this object of the present invention, a stream of air and entrained material owing into a material collection chamber is divided into two portions and the portions are directed to flow along oppositely turning courses. Kinetic energy of the flowing air and entrained material is then dissipated by impinglng the two portions of flowing air and entrained material one against the other within the chamber, so that entrained materials are separated from the air and are deposited in' the chamber.

A further object of the present invention is to selectively vary the liquid retaining capacity of a vvacuum pickup apparatus, in order to adapt the apparatus to particular conditions of use. In realizing this object of the present invention, the housing components of a vacuum pickup apparatus include an extension piece which normally may be coupled to other housing members in a supporting and storage position. When desired or required for expansion of liquid retention capacity, the housing members may be disassembled and the extension housing member inserted between other housing members on reassembly of the apparatus, to provide an enlarged capacity for a material collection chamber.

Yet a further object of the present invention is to separate entrained material from air ilowing into a material collection chamber in accordance with which the air and entrained material is first impinged against a right circular cylindrical obstruction arranged concave toward and closely adjacent an inlet opening through which the air and entrained material flow. By impingement of the inowing air and entrained material against such an obstruction, division and turning of the flow as described briefly above occur and the entrained material is separated from the air in a particularly favorable manner.

Some of the objects and advantages of the invention having been stated, others will appear as the description proceeds, when taken in connection with the accompanying drawings, in Which- FIG. l is a perspective view of a vacuum pickup apparatus yin accordance with the present invention, shown in an environment of use;

BIG. 2 is an enlarged plan View, in partial section, of the apparatus of FIG. 1;

FIG. 3 is an exploded view of certain elements incorporated in FIG. l;

FIG. 4 is an elevation View, in partial section, of the apparatus of FIGS. 1 and 3, taken generally along the line 4--4 in FIG. 2;

FIG. 5 is a View generally similar to FIG. 4, illustrating arrangement of the elements shown in FIG. 3 to provide an enlarged capacity for a material collection chamber of the apparatus of the present invention;

FIG. 6 is a plan view from below, in partial section, taken generally along the line 6--6 in FIG. 5;

FIG. 7 is an enlarged elevation, in partial section, showing a oat switch arrangement incorporated in the apparatus of the present invention;

FIG. 8 is a view generally similar to FIG. 4, showing a second embodiment of the apparatus of the present invention; and

FIG. 9 is a plan view, in section, taken generally along the line 9-9 in FIG. 8.

Referring now more particularly to the drawings two forms of vacuum pickup apparatus which incorporates the present invention are shown, with the rst form being illustrated in FIGS. l-7 and the second form being illustrated in FIGS. 8 and 9. rIhe apparatus of the present invention will be made clear from the discussion which follows, which will proceed first with reference to the embodiment of FIGS. 1-7.

As illustrated in FIG. l, the vacuum pickup apparatus of the present invention, generally indicated by the reference character 10, is useful in the construction field for inducing a ow of air through tubing to be used as an electrical wire conduit, such as tube members 11 and 12 shown to be embedded into concrete fioors and walls of a building structure and to terminate at a junction box 14 cast into the wall. In inducing air flows through such conduits, drawing conductor fishing lines therethrough, the apparatus of the present invention is coupled to a conduit 11 by means of a flexible fiow pipe 15 and an appropriate sealing collar 16 or other means to insure that the pressure differential relied upon for movement of air and entrained material through the conduit 11 is not lost. As shown, `the apparatus 10 is arranged for drawing air and entrained material from the conduit 11, but the apparatus may additionally be arranged to blow air into the conduit 11 as described briefiy hereinafter. The primary concern of the present invention relates to operation as illustrated in FIG. l, where air and entrained material is being drawn from the conduit 11.

As shown more clearly in FIGS. 3-5, the vacuum pickup apparatus 10 has an expansion chamber 18 defined therewithin by the cooperation of separable housing members 19, 20 and 2l. An inlet conduit means 22 extends from the upper surface of one of the separable housing members, namely the housing members 20, for connection of the flexible conduit thereto when the apparatus 10 is operated as a vacuum pickup apparatus. The inlet conduit means 22 has at least a portion within the chamber 18 extending perpendicular to an obstruction as discussed hereinafter and includes an egress opening 24 within the expansion chamber 18, for delivering air and entrained material thereinto during operation of the apparatus l10. Mea-ns are provided communicating with the chamber 18 for inducing a fiow of air therethrough, preferably by the mounting of a vacuum fan apparatus 25 within a second separable housing member 20. The fan 25 may be of a conventional commercially available type, having an electric motor which drives a centrifugal fan rotor in rotation. The fan 25 communi- Cates with the chamber 1-8 through an outlet opening 26 therefrom, positioned above and behind the egress opening 24 and extending through a lower wall 28 of the second separable housing member 20. The fan 25 is secured in position within the enclosing housing member by means of a plurality of bolts extending through the lower wall 28 of the housing member 20 and may be connected with an appropriate source of electrical current of conductors 29 extending through the wall of f the housing member (FIG. 2). An appropriate manually operated on-off switch 30 is provided to give control over operation of the fan' 25.

In accordance with important features of the present invention, flow directing means is provided within the chamber 18 and positioned closely adjacent the egress opening 24 of the inlet conduit means for receiving the inflowing stream of air and entrained material and directing the iiow thereof within the expansion chamber 18. In particular, when the first and second separable housing members 20 and 19 are secured in superposed position by engagement of snap clasps 31 provided on the first housing member 19 with hook members 32 provided on the second housing member 20', operation of the fan induces a fiow of air through the inlet conduit means and through the chamber 18, as indicated by the arrows in FIG. 4, due to the interposition of a sealing gasket 34 between the housing members 19 and 20 and the tub-like configuration of the second housing meinber 20. lnflowing air and entrained material impinges against the interior wall of the first housing member 19, which defines an obstruction having a right circular cylindrical configuration and concave toward the egress opening 24. On impingement of the infiowing air and entrained material against the obstruction provided by the Wall, the infiowing stream of air and entrained material is divided into two portions, with the portions being directed to flow generally opposite to the direction of entrance into the chamber, along oppositely turning courses of flow within the chamber 18 (as shown by fiow arorws in FIG. 6). As the portions continue to move along the turning courses and in arcuate, half-circular, paths around the cylindrical wall of the tub-like first housing member 19, the portions are directed to impinge one against the other within the chamber 18, at a location along the wall diametrically opposite from the egress opening 24. The impingement of the two portions of fiow one against the other results in the kinetic energy of the infiowing air and entrained material being dissipated, so that the heavier entrained material drops out of the air and is deposited in the chamber 18 while the air flows therethrough. For this reason, the expansion chamber 18 is also referred to herein as a material collection chamber or, in specific application, as a water collection chamber.

In order to further protect the fan 25 against entrance of water into the opening 26 through which the fan 25 communicates with the chamber 18, bafiie means including a plate bafiie member 35 are positioned within the chamber 18 and adjacent the outlet opening 26 (FIGS. 4 and 6). The baffle plate 35 is so arranged as to have an opening defined between one side of the plate 35 and the lower wall 28 of the second housing member 20 which is directed oppositely to the direction of the inlet conduit 22. As a result, air flow into the outlet opening 26 is from a direction generally corresponding to the entrance direction of air into the chamber and opposite to the direction of the two turning courses of fiow within the chamber 18 (FIGS. 4 and 6). That is, ow of air from the chamber involves a reverse turning and upward movement from the point of impingement of the two portions one against the other.

Separation of entrained materials other than liquids is further insured by the interposition of an annular filter screen means 36 in the path of air liow from the egress opening 24 to the outlet opening 26, for filtering of entrained solid materials from air fiowing through the chamber 18. Where it is desired that the vacuum pickup apparatus 10 additionally be operated as a vacuum cleaner for collection of dust particles and the like, it is contemplated that a filter paper or filter cloth may be disposed about the screen means 36 to provide effective filtration of small particle entrained solid materials. Recognizing that the vacuum pickup apparatus 10 will not always be used in environments requiring such fine particle filtration, the fan 25 chosen for installation in the apparatus 10 preferably is of the type which has relatively high tolerance for fine particles of entrained solid materials.

It is to be noted that the annular filter screen means 36 cooperates with other structure of the apparatus 10 in certain particular ways. First, the filter screen means 36 is offset within the chamber `18 relative to the sidewalls thereof and generally diametrically opposite to the point of initial impingement of the inflowing stream against the concave surface flow obstruction. Thus the flow of the divided stream along two half-circular paths within the chamber sweeps across the surface of the filter screen means 36, so as to make the apparatus self-cleaning in the sense that material collected on the filter screen means is cleared therefrom and deposited in the chamber. Further, upper portions of the fiow along the arcuate paths is subjected to increasing restriction while lower portions are free to flow beneath the filter screen means. Inasmuch as flow is distributed to the paths of least resistance, the offset relation of the filter screen means additionally serves to direct the oppositely turning courses of flow downwardly into mpingement therebeneath.

In order to provide for ready mobility of the apparatus when used as a construction site, a carrying handle 3-8 preferably is mounted on an upper closure for the second separable housing member 20. By means of the handle 38, an operator of the apparatus 10 may transport the apparatus from point to point to Whatever location use of the apparatus may be required. Further, by removal of the tub-like first housing member 19, the total weight of the portable portion of the apparatus 10` may be reduced to facilitate use of the apparatus as a source of blowing air only. When so used, the flexible conduit is connected to the outlet 39 of the fan 25, and such outlet preferably projects through the sidewall of the second housing member to facilitate such use of the apparatus 10` (FIG. 2).

It is recognized that the use of the apparatus 10 as described to this point, in the pickup of air and entrained material from a conduit 11, may result in the deposition 4of significant quantities of liquid into the material collection chamber 18. Recognizing that operation of the apparatus 10 should not be continued beyond the point at which a maximum quantity of material is deposited in the chamber 18, the apparatus 10 further incorporates a safety control means responsive to the quantity of material retained within the tub-like first housing member 19. Preferably, the safety control means includes a switch 40 (FIG. 7) housed within the second housing member 20 and electrically connected in series with the manual switch 30. The switch 40I is operatively connected with a float ball 41, mounted at the end of a pivot arm 42 for movement beneath the lower wall 28 of the housing member 19. Motion of the float ball 41 is passed to the switch 40 by means of a push pin 44 penetrating the lower wall 28. Upon the quantity of material retained within the chamber exceeding a predetermined maximum preferably so related to the position of the egress opening 24 as to insure that water does not reach the level thereof, the float ball 41 is raised, the contacts of the switch 40 are opened and further energization of the fan 25 is prevented.

It is recognized that significant quantities of liquid will be encountered in instances where construction has been interrupted by periods of stormy weather, and will require that the capacity of the apparatus 10 to retain Water drawn into the chamber 18 be enlarged in order to maintain efiicient use of the apparatus 10. The present invention contemplates that enlargement of the capacity of the material receiving chamber 18 be accomplished in a particularly favorable manner, and with enhancement of other features of the apparatus 10. In particular, the third separable housing member 21 is particularly adapted, in accordance with the present invention, for performing two distinct functions. First, the third separable housing member 21 may normally be coupled to the tub-like first separable housing 19, as a support therefor and to provide a storage location for apparatus accessories, as pointed out more fully hereinafter. However, the third housing member 21 is constructed and arranged for inter position between the first and second housing members upon the housing members being separated and to serve a second function by cooperation with the first and second housing members when reassembled to define a deposited materials receptacle of enlarged capacity. These ends are accomplished by forming the third separable housing member 21 as an open ended drum. That is, the third housing member 21 has a right circular cylindrical wall in similarity to the housing members 19 and 20. In distinction therefrom, however, the ends of the third housing member 21 are both open. One end has formed therein a plurality of radially inwardly extending ear portions 45, for purposes pointed out more fully hereinafter, and the housing member has clasps 31 and hooks 32 mounted thereon in similarity to the clasps 31 and hooks 32 of the first and second housing members 19 6 and 20. By the provision of the clasps and hooks, the three housing members 19, 20, 2/1 may normally be stacked as shown in FIG. 4, but may be separated and reassembled in the configuration shown in FIG. 5 where it is desired to provide a chamber 18 of enlarged capacity.

As mentioned briefiy above, the third housing member 21 provides a storage receptacle for apparatus acessories. In particular, an inner tray 50 is provided as a portion of the apparatus 10 and preferably is constructed with a diameter such that it will rest upon the radially inwardly projecting ears 45 when positioned within the third housing member 21. The removable tray 50 provides a ready storage space for line pulling acessories such as foam discs, packages of nylon cord, and the like which are protected against contamination by the normal attachment of the third housing member 21 to the second housing member 20. Desirably, the enclosure of the volume within the third housing member 21 is normally completed by the positioning therewithin of a false bottom 51, sized to rest on the radially inwardly projecting ears 45 and normally secured thereto by bolts and thumb screws. As will be understood, use of the false bottom 51 permits storage of accessories Within the third housing member 21 without regard to the use of the removable tray 50, and vice versa.

The present invention contemplates that the advantage of an at least partially cylinderical obstruction and the method of vacuum pickup disclosed herein may be derived by structural arrangement modified from that discussed to this point. In particular, a second form of apparatus in accordance with the present invention is shown in FIGS. 8 and 9, and generally indicated therein by the reference character 100. Portions of the apparatus corresponding to portions of the apparatus 10 discussed to this point have been identied by similar reference characters of the one hundred series, for purposes of convenience in cornparing the structural elements of the two forms of apparatus. The distinctions between the two forms of apparatus lie principally in the relationships of the egress opening 124 to the interior wall of the first housing member 119 and to the baffie means 135 which directs the course of air flow into the outlet 126.

In particular, the inlet conduit 122 terminates generally centrally of the expansion chamber 118, and -closely adjacent an obstruction defined by a reduced diameter tubular portion 160. Obstruction of fiow from the inlet opening 124 by the interior wall of the tubular portion 160 results in division and turning of inflowing air and entrained materials generally as discussed above, as indicated by the fiow line arrows in FIGS. 8 and 9. In other respects, operation of the apparatus 100 is generally as described above with reference to the apparatus 10.

In the drawings and specification, there have been set forth preferred embodiments of the invention, and although specilic terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

What is claimed is:

1. A vacuum pickup apparatus comprising means defining an upright expansion chamber and an upright cylindrical concave surface fiow obstruction therein,

means communicatively connected with said expansion chamber and including a vacuum unit mounted on top of the expansion chamber for inducing a flow of air therethrough, and

inlet means positioned in an upper portion of said expansion chamber and located adjacent said cylindrical upright concave surface for directing a high velocity stream of air and entrained material in a predetermined entrance direction into impingement against said cylindrical concave surface flow obstruction, for dividing the stream into two portions, and for diverting the portions along apposite courses of ow along said cylindrical concave surface into impingement with each other within the expansion chamber in a direction generally opposite to the entrance direction of the stream into the expansion chamber to effect separation of entrained materials, whereby the kinetic energy of the infiowing stream of air and entrained materials is dissipated first by impingement against the cylindrical concave surface obstruction and thereafter by impingement of the divided portions one against the other within the expansion chamber and entrained materials remain in the expansion chamber while air flows therethrough.

2. A vacuum pickup apparatus according to claim 1 wherein said cylindrical concave surface flow obstruction defines a wall portion of said expansion chamber.

3. A vacuum pickup apparatus according to claim 1 where in said cylindrical concave surface flow obstruction has at least a portion thereof positioned generally centrally of said expansion chamber.

`4. A vacuum pickup aparatus according to claim 1 wherein said expansion chamber has an outlet opening and further comprising filter means interposed in the path of air fiow from the location of impingement of said two portions with each other within said expansion chamber to said outlet opening for screening of entrained material from air fiowing through the expansion chamber.

5. A vacuum pickup apparatus according to claim 1 wherein said expansion chamber has an outlet opening and further comprising baffle means positioned within said expansion chamber adjacent said outlet opening for directing air fiow thereinto and from said expansion chamber in a direction opposite to the direction of said Opposite courses of fiow.

6. A vacuum pickup apparatus according to claim 1 wherein said first recited means comprises first and second separable housing members normally coupled together in superposed relation and cooperating for defining said expansion chamber, said first housing member being of tub-like configuration and providing a receptacle for deposited materials and said second housing member providing an enclosure for said air fiow inducing means.

7. A vacuum pickup apparatus according to claim 6 wherein said first recited means further comprises a third separable housing member normally coupled to said first housing member and functioning as a support therefor, said third housing member being constructed and arranged for selective interposition between said first and second housing members for defining a deposited materials receptacle of enlarged capacity.

8. A vacuum pickup apparatus according to claim 1 wherein said last recited means comprises an inlet conduit having at least a portion thereof extending within said expansion, chamber and directed generally perpendicular to said cylindrical concave surface fiow obstruction and terminating in an egress opening closely adjacent said cylindrical concave surface tiow obstruction.

9. A vacuum pickup apparatus according to claim 8 wherein said expansion chamber has an outlet opening disposed behind and above said egres opening of said inlet conduit.

10. A vacuum pickup apparatus according to claim 8 wherein said egress opening of said inlet conduit and at least a portion of said concave surface fiow obstruction are positioned generally centrally of said expansion chamber.

11. A vacuum pickup apparatus according to claim 8 wherein said expansion chamber has an outlet opening and further comprising annular filter means within said eX- pansion chamber and interposed in the flow path of the stream from said egress opening of said inlet conduit to said outlet opening of said expansion chamber so as to be swept by the divided portions of the stream for removing accumulated material from the surface thereof.

12. A vacuum pickup apparatus according to claim l1 wherein said annular filter means is positioned in offset relation within said expansion chamber and is located be- 8 hind said egress opening of said inlet conduit so as to increasingly restrict the paths of travel of upper portions of the divided stream within said expansion chamber while lower portions thereof are passed along substantially unrestricted paths of travel to thus cause substantial portions of the iiow of the two portions of the stream to follow the path of least resistance downwardly into impingement with each other.

13. A vacuum water pickup apparatus comprising inlet conduit means for passage of a stream of air and entrained water and including an egress opening from which the stream of air and entrained water flow,

upright housing means in an upper portion of which said egress opening of said inlet conduit means is positioned, said housing means enclosing said egress opening and defining a water collection expansion chamber having an upright right circular cylindrical concave wall surface positioned closely adjacent and facing toward said egress opening, said inlet conduit means providing for impingement of the stream of air and entrained water against said concave wall surface and for division of impinging air and entrained water into two portions fiowing along oppositely turning courses of flow along said cylindrical concave surface within the expansion chamber in a direction generally opposite the entrance direction of the stream into the expansion chamber and for dissipation of the kinetic energy of the air and entrained water by impingement of the portions one against the other within the expansion chamber so that water is deposited therein while air flows therethrough, and

means including a vacuum unit mounted on top of said housing means for inducing a fiow of air through said inlet conduit means and housing means for entraining water and depositing entrained water in said expansion chamber.

14. A vacuum water pickup apparatus according to claim 13 further comprising control means including a switch operatively associated with said air fiow inducing means for interrupting operation of said vacuum apparatus when the level of water in said water collection expansion chamber reaches a predetermined level below said egress opening of said inlet conduit means, said control means further including float means within said water collection expansion chamber for actuating said switch and being positioned at a lower level than said egress opening.

15. A vacuum water pickup apparatus according to claim 13 wherein said housing means comprises first and second separable housing members normally coupled together in superposed relation and cooperating for defining said expansion chamber, said first housing member being of tub-like, right circular cylindrical, configuration and providing a receptable for deposited water, and further wherein said conduit means egress opening is disposed immediately adjacent the interior wall surface of said first member so that said first member defines said cylindrical concave wall surface for impingement and division of air and entrained water.

16. A vacuum water pickup apparatus according to claim 13 wherein said housing means comprises an openended tubular portion of right circular cylindrical configuration positioned medially of said chamber and further wherein said conduit means egress opening is disposed immediately adjacent the interior wall surface of said tubular portion so that said tubular portion defines said cylindrical concave wall surface for impingement and division of air and entrained water.

References Cited UNITED STATES PATENTS 2,295,984 9/1942 Wilson 55-334 2,327,553 S/l943 lonselle l5-327 l) (Other references ou following page) 9 UNITED STATES PATENTS Doyle 15-327 R Barba 15-327 R Congdon 15-319 Hayes et a1 55- 337 5 Thurman 55-468 Ortega 15-353 Gerstmann 15-353 Filley 55--462 10 FOREIGN PATENTS 1,094,603 12/1954 France.

FRANK W. LUTTER, Primary Examiner B. NOZICK, Assistant Examiner U.S. C1. X.R.

UNTTED STATES PATENT oFFIcE CERTIFICATE OF CGRRECTION Patent No, 3 618, 297 Dated NOVembeI 9, 1971 Inventor(5) J. C. Hamrck It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 32, second Instance of "membersH should be "member". Column 4, line 11, "arorws" should be "arrows". Column 5, line 4, "as" should be --at. Column 6, line 27, I'cylinder'ical" should be cylIndrcal-; line 74, CLAIM 1, "apposite" should be "opposite". Column 7, line 16, CLAIM 3, "Where in should be wherein, line 52, CLAIM 8, delete the comma after "expansion", line 58, CLAIM 9, "egress" should be "egress" Signed and sealed this 25th day o' April 1972.

(SEAL) Attest:

EDWARD MQFLETCHERJR. ROBERT GOTTSCHALK Attestng Officer Commissioner of Patents FORM P04050 (1G-69) oscoMM-oc soave-Pes l 

